Dinosaur Jr frontman/guitar butcher J Mascis isn’t known as the most talkative man in rock, so it’s a rare treat to see he’s guesting on today’s episode of “WTF,” the Marc Maron-hosted podcast that has nicely expanded from its comedians-talking-about-comedy roots to include the occasional musical guest. True to form, Maron chats up Mascis and gets him to deliver an acoustic performance, too.